Additionally, some antigenic competition occurs in these complex mixtures. As might be expected, large individual variations in response occur between animals. Factors other than antibodies must be responsible for the prolonged immunity seen in practice. Studies however suggest that antibody levels peak about 36 days after vaccination and are maintained up to 90 days before declining rapidly. They are normally administered in two doses and elicit responses that are protective for at least a year. Polyvalent clostridial vaccines contain a complex mixture of toxoids and bacterins from up to eight different species. perfringens vaccine should be administered to pregnant ewes in late pregnancy to ensure adequate levels of antibodies in colostrum and protection of lambs for four to six weeks. This leads to sudden death in weaned lambs on a high carbohydrate diet.
This results in abrupt changes in the intestinal microbiota and clostridial proliferation. It usually affects lambs over one month of age and is often precipitated by a change of feed. perfringens type D causes enterotoxemia (overeating disease) and pulpy kidney disease. Vaccination of the ewe in late pregnancy, four weeks before lambing, offers protection. It may be triggered by changes in feed or receiving too much milk. perfringens type C causes a hemorrhagic enteritis (“bloody scours”) in suckling lambs during the first few weeks of life. Seven toxinotypes (A–E) have been identified.
These Clostridial organisms can grow rapidly in an animal and secrete a complex mixture of toxins and enzymes. This protects against enterotoxemia caused by Clostridium perfringens types C and D and also tetanus caused by Clostridium tetani. Specifically, the preferred vaccine is CD-T toxoid. The most important vaccines given routinely to sheep and lambs in North America are those used to protect against Clostridial diseases.
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